Hi Everyone,

One list member asked me a question off-list triggered by my Bald Eagle fishing for trout posting, and I thought the information might be of interest to others, so am posting to this list.

The basic question was whether the Osprey were able to defend their nests against the Bald Eagles, since both exist along the river. (This question also ties in with an earlier post postulating Great Blue Herons nesting near Ospreys to possibly get the benefit of the Ospreys' willingness to defend their nests vigorously.)

My answer is just based on my observations - I do not have any scientifically rigorous data. First of all, there are few eagles along the 35 miles of river we float. We have seen one or two in the same area each year for the last three or four years, fully mature birds. This year we saw a pair flying together, and on a different day and perhaps ten or fifteen miles from where we saw the pair, I saw another mature bird. This bird could have been a third bird (but could also have been one of the pair ranging further from home turf). I have seen no indication at all of eagle predation on osprey nests, and the osprey nests in the last few years have become more numerous and quite successful - a high percentage of the nests have had healthy young over the last three years when I've been paying closer attention. However, with a higher eagle to osprey ratio, it seems logical that the osprey chicks would make tempting targets for the eagles.

I have seen Osprey harrassing eagles, so the Ospreys certainly appear to view the eagles as a potential source of problems. The third eagle I saw this year was in fact being actively bothered by a diving Osprey when I first saw it. Two years ago both adult Ospreys in the nest near our camp went on an intense dive-bombing campaign of a Golden Eagle that landed several hundred yards away on the other side of the river at the site of a kill. In that case, the eagle was so bothered by the attacks that it dragged its prey into a tall sagebrush patch to provide some overhead cover. I have on two occasions witnessed vigorous diving attacks on Great Blue Herons who were flying along the river near Osprey nests. So at least on the Deschutes, it doesn't seem likely that a Great Blue Heron would be able to establish a nest in close proximity to an Osprey nest.

On the Deschutes, my best guess would be that the eagles primarily focus on fish as prey, since they are plentiful and eagles' preferred prey is generally considered to be fish. The Osprey appear quite capable and willing to defend a wide perimeter around their nests when anything they perceive to be a threat comes near. Although the Osprey vocalize warnings to fishermen or rafters that come near their nests, and occasionally fly around (from a good distance) human intruders to 'size them up' I've never seen one actually dive at a person. I would guess that they are habituated to the large numbers of people floating the river in the summer and don't perceive them to be threats, although they keep an active watch just in case.

John Tubbs
Snoqualmie, WA
johntubbs at comcast.net
www.tubbsphoto.com